It is known for objects to be bound by means of a band which is positioned as a loop around the object, the ends of said loop then being fixedly connected to one another by a lock. If a large number of binding operations are to be carried out at a workstation, as is the case, for example, in the production of cable harnesses, use is made of largely automatically operating tools which are assigned magazines for the locks and the band. Whereas small magazines may be arranged on the tool itself, large magazines are kept stationary. In order for it to be possible for the locks to be fed to the tool from such stationary magazines, the locks are designed as a more or less endless lock chain by the individual locks being retained, for example, on a carrier strip or being connected directly to one another by material crosspieces which are severed before the individual lock is used. In the case of known tools, the conveying path for the lock chain between the magazine and tool is formed by a flexible tube. If the connection between the individual locks is firm enough, it may be possible, if appropriate, to dispense with the protection given by such a flexible tube. The conveying path is then formed by the lock chain as such. In each case, considerable forces may be necessary in order to move the lock chain up into the tool if, for example, the flexible tube forming the conveying path is curved or the lock chain, before it passes into the tool, is angled in relation to the guide channel accommodating it in the tool. In the case of known tools, a pneumatic drive is provided for this purpose. This has the property of comparatively large forces being available for brief driving tasks, as occur during the brief advancement of the lock strip between two binding operations. A pneumatic drive, however, has disadvantages in comparison with an electric drive, for example in respect of the weight and the dimensions of the tool and the pressure-medium feed. It is also the case that the energy consumption and the noise development are unfavourable in pneumatic tools. Electric drives on binding tools are also known. However, if they are not likewise to be heavy and bulky, these have the disadvantage that they cannot supply high power for a brief period, which is required for moving the lock chain up into the tool. For a demonstration of the prior art, you are referred to the brochure entitled xe2x80x9cAutomatische Bxc3xcndel-und Verschluxcex2werkzeuge [Automatic bundling and closure tools] Autotool/Tytontoolxe2x80x9d from Paul Hellermann GmbH, EP-B 303723, EP-B 565968 and U.S. Pat. No. 4,610,067. In the case of EP-A 297 337 and EP-A 565 968, the advancement is brought about by the actuation of a hand lever.
Taking as the departure point the prior art mentioned in the preamble of claim 1, namely the abovedescribed brochure, the object of the invention is to make it possible to use an electric drive in the case of tool arrangements with a stationary lock magazine. The solution according to the invention resides in the features of claim 1 and preferably those of the subclaims.
Provision is accordingly made for the conveying drive provided to be a spring which can be subjected to stressing by the electric tool drive. The spring may easily be dimensioned such that it applies the necessary advancement forces. It may also be subjected to stressing by a low-torque motor, because all that this requires is suitable dimensioning of a reduction gear mechanism located between the motor and the spring.
Expediently provided for the purpose of subjecting the lock chain to the advancement force is an advancement engagement element which is arranged on the guide channel of the tool and is guided such that it can be moved in the direction thereof. The advancement engagement element is subjected to loading in the advancement direction exclusively by the spring during the advancement phase. In another part of the operating cycle, namely when a binding operation has been completed and a new lock has to be provided, it is connected to a restoring means which is moved counter to the advancement direction by the tool drive. Said restoring means moves the advancement engagement element back by at least the longitudinal dimension of a lock, in order that it can engage with the following lock in the subsequent advancement operation.
The restoring means is expediently a rotary cam, because such an element is straightforward to provide in design terms and can easily be engaged with, and disengaged from, the advancement engagement element or an interposed transmission element. Such a transmission element between the rotary cam and the advancement engagement element is designed, according to the invention, as a multi-armed lever, of which one lever arm interacts with the rotary cam, while a second lever arm is connected to the spring and a third lever arm is connected to the advancement engagement element. The arrangement may also be such that one lever arm performs a number of the functions which have just been specified.
In a particularly preferred embodiment, the rotary cam periodically passes into the pivoting region of the lever arm assigned to it and also leaves said pivoting region again. As soon as the rotary cam engages with the lever arm, it rotates it in such a way that the spring is subjected to stressing and the advancement engagement element is retracted. As soon as it leaves the pivoting region of the lever arm, the spring, and thus the conveying drive, is disengaged. The advancement engagement element engages with the next lock and moves the latter forwards. Since this lock is fixedly connected to the lock chain following it, the latter is likewise moved up.
The spring force is preferably then maintained in order for the lock located in front of the advancement engagement element, as seen in the advancement direction, or the foremost lock of the number of locks located in front of the same, to be forced into that position in which it is ready for the following binding operation and in order for it, if appropriate, also to be retained in this position.
According to a particular feature of the invention, which possibly merits protection independently of the features explained above, the advancement engagement element is arranged on a carriage which is guided such that it can be moved essentially parallel to the guide channel, and which is also equipped with a device for separating the locks from one another. This is based on the idea that the as yet unseparated locks located in the vicinity of the advancement engagement element are positioned very precisely in relation to the advancement engagement element, and a separating device, the position of which is fixed in relation to the advancement engagement element, can thus carry out the separating operation at a very precisely determinable location of the lock chain. This is important, in particular, in the cases in which the locks are connected to one another by very short crosspieces, which have to be cut in a correspondingly precise manner.